capture and save image from webcam using v4l2

[bibhukalyana]

Hi everyone,
I am using fedora 14 64bit os(kernel 2.6.35). I want to capture image from web cam using v4l2 .I tried as

struct v4l2_capability cap;
    int fd = open(dev_name,O_RDWR);
    int err = ioctl(fd,VIDIOC_QUERYCAP , &cap);

    struct v4l2_format format;
    format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    format.fmt.pix.width = 640;
    format.fmt.pix.height = 480;
    format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    err = ioctl(fd, VIDIOC_S_FMT, &format);

    struct v4l2_requestbuffers req;
    void **mem;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.count = 4;
    req.memory = V4L2_MEMORY_MMAP;
    err = ioctl(fd,VIDIOC_REQBUFS,&req);

    mem =(void **) malloc(req.count*(sizeof(*mem)));

    struct v4l2_buffer buffer;
    unsigned int i;
    for(i = 0;i < req.count;i++)
    {
        buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buffer.memory = V4L2_MEMORY_MMAP;
        buffer.index = i;
        err = ioctl(fd,VIDIOC_QUERYBUF,&buffer);

        mem[i] = mmap(0,buffer.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,buffer.m.offset);

    }

    int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    for(i = 0 ; i < req.count ; i++)
    {
        buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buffer.memory = V4L2_MEMORY_MMAP;
        buffer.index = i;
        err = ioctl(fd,VIDIOC_QBUF,&buffer);
    }
    err= ioctl(fd,VIDIOC_STREAMON,&type);

    buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buffer.memory = V4L2_MEMORY_MMAP;
    err=ioctl(fd,VIDIOC_DQBUF,&buffer);
    process_buffer(mem[buffer.index],buffer);

in process_buffer, i suppose to save the image.But when i am trying to save the color of image is not proper. I think the image datas are in 16bit per pixel.
Can any one tell how to save it ?

thanks

[rabinnh]

If you attach a dump of the buffer, it would be a lot easier for someone to help. If you can write it as a TIFF so much the better.

OTOH, if you are just trying to capture an image from a Web cam, why not just access via HTTP? Or is it actually a USB cam?

[bibhukalyana]

Yes it is a usb logitech web cam.
How i will access via HTTP ?
I tried to run v4lgrab.c (inside linux kernel source -: linux-2.6.35/Documentation/video4linux).But it is showing "/dev/video0 is not a video4linux device".